In this topic, we will be learning about one of the most important aspects of sustainability in
landscapes in the arid southwest, water conservation and irrigation. Before viewing the video on
landscape irrigation and water conservation, read the article about xeriscaping.
After reading the article and watching the video, you should be able to answer the following
questions:
1. Why is irrigation required in southwestern home landscapes and gardens? What are the
major determinants that determine how much water a plant needs to thrive? What does
the term transpiration mean?
2. What is the different between xeric and mesic landscape plants with respect to their
water use?
3. What are the two basics types of irrigation used in landscapes and how are they
utilized?
4. What is the typical flow rate for emitters in a drip irrigation system? How does this
compare with the flow rate of a sprinkler head? What is the difference between these
two systems with regard to the duration of irrigation?
5. What are major components of any irrigation system? How do the components differ
between a drip and sprinkler irrigation system?
6. What are the 3 types of sprinkler heads and how are they used to supply overhead
irrigation? Which sprinkler heads would be used to irrigate a small area and which are
used to irrigate a large area?
7. Why are filtration devises and pressure regulators required in a drip irrigation systems?
8. What types of tools are required to work with and/or repair irrigation systems? What is
the difference between working with PVC pipe used in sprinkler irrigation and the drip
pipe used in drip irrigation?
9. What is the function of an irrigation valve, backflow prevention device and an irrigation
controller? What is a solenoid valve? Is a solenoid valve normally closed or open when
not activated by the irrigation controller?
10. How does weather affect how much water a plant needs? What types of weather require
an increase in the frequency of irrigation?
11. What ranking would you give the following plants with regard to the amount of water
needed for growth: turf, trees and shrubs and vegetables?
12. What does the term xeriscape mean? What are the seven principles of xeriscaping that
can be used to promote water conservation in landscapes? Which are the most
important in our area?
13. What is mulch? What is the difference between an organic and inorganic mulch? What
types of mulch is typically used in landscapes in the Phoenix area? What are the
advantages to using mulch as part of a landscape or garden?
Video: Landscape Irrigation and Water Conservation
Introduction
● Key aspects and key points relative to irrigation and water conservation in the Desert
southwest
How do plants respond to water loss
● Plants respond to water loss from their leaves by absorbing water from the soil through
their roots
● Up to 99% of water absorbed by a plant’s roots travels through the vascular system
called xylem and is lost to the atmosphere through open stoma or pores on the surface
of leaves
● This evaporation of water from leaf stomata is called transpiration
○ It is an important part that can help maintain leaf temperatures as much as 10 to
degrees cooler than ambient temperatures during hot summer days
● Amount of water transpired by landscape plants during our hot summer days is often
underappreciated
Water use
● Two most important determinants of plant water use
○ Plant size
○ Leaf size
● Mesic or water-loving plants require more water because they have larger leaves
● In contrast, xeric or low water use plants of similar size generally require less water than
mesic plants because of some specialized adaptations that lower their overall amounts
of water loss through transpiration
Rain
● Deserts of central Arizona typically receives less than 10 inches of rain each year
● In contrast potential evapotranspiration, which is cumulative measure of the amounts of
water lost from both soil plants in the desert, is about 9 times greater or 90 inches a year
● This extreme disparity between natural rainfall and water loss means that nearly all our
managed landscapes in the desert southwest needs some form of supplemental water
or irrigation
Daily water demands
● Daily water demands of plants in our desert climate vary throughout the year with the
changing of the seasons
● Highest during the summer because of our high summer temperatures, low humidities
and intense sunlight
● Lowest during the winter
● Because of this, the amount and frequencies of irrigation water we give to our landscape
gardens must be gradually increasing during the spring and decreased during the fall
Two basic types of irrigation delivery systems
1. Overhead (sprinkler) irrigation system
2. Low volume or drip irrigation
3. Flood irrigation system
● Was once common in the phoenix area is now seldom seen
Overhead (sprinkler) irrigation system
● Provides water from above in a manner that stimulated a gentle falling rain
● Technology became commonplace during the 1960’s
● Its expansion in use correlates with the development of high-density rigid plastics such
as polyvinyl chloride or PVC pipe
● In the desert Southwest, it is most commonly used to irrigate turf grass lawns because of
its ability to distribute water broadly and evenly across a relatively large surface area
● Because this type of irrigation system literally throws water into the air in spray-like or
stream like patterns the application of water including the selection and placement of
sprinkler heads must be precise
● Timing of water delivery should be during calm conditions because wind can deform the
sprinkler throw pattern and cause water to fall on non targets
● Flow-rate is most typically one-half to 5 gallons per minute per sprinkler head head
● Different types of sprinkler heads for lawns and large turf areas are able to throw water
to distances ranging from 5 to 50
3 types of overhead sprinkler system watering devices
● Spray head
○ Throw out water in a fan-like distribution pattern to distances ranging from 5 to 15
feet
○ Suitable for irrigating relatively small areas of turf grass lawn
○ Arc of the spray pattern is fixed by the spray head nozzle type and can range in
design from 45 to 360 degrees
● Rotating head
○ Generates single stream of water
○ Water stream moves around in an adjustable pattern that is
■ made possible by a mechanical gear located within the body of the
sprinkler head
○ can throw out a stream of water to distances ranging from 15-50 ft
○ Good choices for irrigating medium and large areas of turf grass lawn
● Impact head
○ Uses an external rotating arm to pulse and rotate its single stream of water also
in an adjustable pattern
○ Both the impact and rotating heads can throw out a stream of water to distances
ranging from 15-50 ft
○ Good choices for irrigating medium and large areas of turf grass lawn
Low Volume or drip irrigation system
● Delivers water precisely to a desired location through devices called emitters
● Emitters have delivery rates that are generally equal to or less than the rate of which
water infiltrates into soil
● Modern drip irrigation became widespread in the 1980’s
● Now the most common way to irrigate landscape trees and shrubs in arizona
● Technologies correlates well with the development of low density plastics (such as
polyethylene or PE tubing) that is highly flexible
● Properly designed and maintained system can conserve water by upwards to 80 to 90
percent by applying it in a highly efficient and controlled manner directly to soil
containing plant roots
● Flow rate is typically 1 to 4 gallons of water per emitter
● Drip emitters operate by distributing water through small orifices or opening that are
subject to clogging unless a drip irrigation system is fit with filtration device or y filter
● Needs some form of pressure regulating or water flow control device to slow the flow of
water and regulate system operating pressures to below 25 pounds per square inch
How to work with irrigation system and tools
● In order to work with PVC pipe you need these tools
○ A ratcheted pipe cutter, Teflon tape, a pipe wrench, both liquid primer solvent and
liquid glue cement and a clean rag
● PVC pipe is cute with ratchet pipe cutters
1. Place pipe in slot and using ratcheted motion cut down the pipe with the
handheld motion going forward
● Will give you a nice clean cut
● If pipe is greater than one inch, you’ll have to use a hacksaw
● Gluing together irrigation pipe
1. Clean off dirt and debris off pipe
2. Take irrigation solvent and apply to edge of surface you’ll be gluing to soften pipe
3. Take your glue and apply it completely around the surface
4. Connect the two fittings together completely
5. Give it a quarter turn to make sure connection is solid
6. Wipe off any excess glue
7. Wait about half an hour
Working with polyethylene or drip pipe
● Polyethylene is very flexible
● Use a modified pipe cutter to cut the pipe
● Only using a hand forced compression motion to apply the fitting to pipe
● Hand punch to apply the hole which you will insert the drip emitter
Three other components critical for irrigation system
● Irrigation valve
○ Prevents or allows water to pass from the pressurized irrigation supply pipe into
the lateral piping system that delivers water to irrigation system or emitters
○ Can be manually or automatically operated
○ Automatic ones use solenoid valves which are constructed of high density
plastics
■ Solenoid valves (like the ¾ in. size) consists of a cylinder shape solenoid
that rests on top of a body comprised of a single chamber divided in half
by a plastic or rubberized diaphragm
○ Solenoid valves are normally closed unless activated by a low-voltage electrical
current sent from the irrigation controller
○ inside the valve solenoid is a piston and a spring
■ Piston is normally extended preventing water from getting past the valve
diaphragm
■ When charged by electricity,the spring becomes a tiny magnet, it coils
tighter as a result of its own magnetic properties and pulls the piston
backward allowing the diaphragm to be pushed out of the way by the
force of the incoming water which in turn allows water to rush freely
○ When the current causing solenoid spring to coil is turned off by irrigation
controller, the piston returns to its original position and seals the diaphragm shut
● Backflow prevention device
○ Legally required and necessary part of every irrigation system
■ Especially if the water comes from a potable or drinkable source
○ Device allows water to go one direction but prevents it from going backwards in
the opposite direction
○ Arizona state laws require all devices regardless of height to be located at a
height of 6 inches above the elevation of the highest sprinkler head or drip
immeter
● Irrigation controller
○ Main purpose is to regulate the frequency and duration of waterings allowed by
an irrigation valve
○ Companies that make excellent residential irrigation: hunter, rain bird, toro, and
iratrole
○ Receives incoming power at 110 volts and using a voltage regulator distributes
the electrical current at 24 volts through the irrigation wire to the irrigation valve
○ A single white colored common ground wire is run in series to all irrigation valves
○ In addition each valve receives an electrical current
○ Make sure its generally shades from the sont and relatively close to a 110 volt
power source
Frequency and duration of watering
● Varies with the types of plants being grown and changing weather and seasons
○ Bermuda grass needs to be water with about 2 to 3 inches of rainfall equivalent
each week during the summer
■ Might not need little to no water depending on amount of rainfall in the
winter
■ Or weather it’s been overseeded
● Drip irrigated trees and shrubs might need supplemental water for two to six hours once
every five to seven days during the summer and once per month depending on rainfall
patterns in the winter
● Most water needy plants are found in vegetable gardens
○ Vegetable garden plants will need to be watered heavily daily
■ Most typically in the late morning hours
■ In the winter time, a winter garden may be watered every several days.
Amounts of water will be dictated by the precipitation both in terms of
frequency and intensity
■ How to know if garden is getting enough water?
● Test soil for moisture content. Use your hand to dig down a couple
inches and if the soil is adequately moist then your gardens water
schedule is good
Xeriscape
● A term coined in the early 1980’s originating in Denver Colorado at a time of severe
drought
● Derived from the greek
○ Literally means a dry view
● Xeriscaping is a set of 7 principles that guide and shape the practices of design
installation and maintenance of landscape gardens in a manner that conserves water
● Two of the principles especially important
○ Use of mulches
○ Intentional selection and use of drought tolerant plants that are especially
adapted to withstand in AZ
Practice of mulching
● Place organic materials (shredded recycled landscape tree or shrub clippings)
● or inorganic materials such as decomposing granite or gravel.
● Place about 2 inches over the surfaces of landscape soil to create a layer of resistance
to water loss from the soil to the air by evaporation
● Research has shown that the use of muches can reduce water evaporation from soil by
as much as 90% when properly applied and maintained
● Mulches also help tree and shrub root growth by moderating soil temperatures from
extremes of summer heat and winter cold
Use of drought tolerant plants
● Such as desert native shrubs and cacti is an effective xeriscape design practice
● Desert tress: blue palo verde and mesquite
○ Conserves water growing leaves that are very small, minimizing water loss
● Cacti and agave, grow internally enormous cells that mostly configured to store water
during times of water scarcity
